Laminate films are often used in the packaging of food products and may have easy-open features, or provide for reclosable features, or both. Reclosable features may be provided at the seal of a bag where it is also opened, and upon opening the package the reclose feature delaminates to expose an adhesive layer used in resealing the package. Typically upon opening, the adhesive layer will remain attached to one or both sides of a film laminate such that the adhesive is often facing the food product side of a package interior, and susceptible to contamination from the food product, thus decreasing its adhesive properties.
Multiple layer films are known that do not have reclosable or adhesive features. U.S. Pat. No. 6,913,809 provides for a lap sealed closure for a bag with a peel layer for opening, where the bag is at least a three layer film that consists of a seal layer and a barrier layer, with a peel layer positioned between the two. When the bag ends are brought together in an overlapping manner to form a lap seal, the seal layer on one side is in contact with the barrier layer of the other side and is sealed together, and when opened the peel layer is separated from the other layers. The peel layer is designed to tear within the layer itself or to tear at its interface with the adjacent layers to make the bag easy to open. However, once these multiple layer film bags are opened, they cannot be easily resealed.
There are many reclosable, adhesive systems known in the art that provide for resealing packages after opening, however the adhesive side is typically exposed towards the package interior where the food product is located, thus presenting a possibility of contamination of the adhesive with food product particles. Furthermore, the known adhesive-reclosure systems are primarily used with fin seal closures. U.S. Pat. No. 5,382,472 provides a packaging material where only the ends of the film layer contain a pressure sensitive adhesive (PSA) layer positioned between two adjacent layers of film made in a side-by-side coextrusion, to provide the resealable seal. The adjacent layers of film are sealed to each other in a fin seal arrangement, and upon opening, the heat-sealable polymer layers remain sealed to one another and peel apart instead at the PSA layer and one of the heat-sealable polymer layers. The bag itself is made up of one or two layers of a material, with just the resealable seal ends containing the at least three layer PSA configuration. Manufacturing a bag with a variation of layers throughout makes the manufacturing process more complex and time-consuming, in addition to the added expense of additional manufacturing steps required to make the multiple layer film only at the ends. Furthermore, once the PSA layer is exposed it is oriented towards the interior of the package, which may be susceptible to picking up food product particles along the PSA layer and thus causing it to lose its adhesion strength for subsequent reclosures.
U.S. Pat. No. 6,502,986 provides a package with a resealable end closure. The package is heat-sealed to form a fin-seal at its end closure, where the ends of a flexible sheet are heat-sealed together and the sheet may comprise one or more layers. Adjacent to the end seal at one end of the package a resealable seal is also formed. When the end seal is peeled apart to open the package, the resealable seal is also separated at an area of a PSA, while heat seal coatings applied over the PSA and to the opposite inner surface of the other end of the sheet remain sealed to one another; thus some amount of PSA remains on one or both sides of the interior flexible sheets with the PSA exposed towards the package interior. This package requires additional process steps to add a PSA between the ends of the sheet, as well as potentially losing the adhesion strength of the PSA due to the PSA being oriented towards the package interior and the food product.
U.S. Pat. No. 5,089,320 discloses a package where an adhesive layer is coated onto a substrate layer used for flexible packaging. The adhesive layer may be coated only in the area where the package is to be opened or may be coextruded with the substrate layer throughout the film, and is further covered by and/or coextruded with a skin layer placed over the adhesive layer. The package is sealed to itself, and when it is opened at the adhesive layer area it is broken apart at the skin layer, thus exposing the adhesive, either between the adhesive and skin layer, or between the substrate and adhesive, or both. The skin layer seals to itself, thus forming a fin seal arrangement. The adhesive layer is oriented towards the interior of the package and may be susceptible to contamination from food, thus losing its adhesion properties. Furthermore, the manufacture of the package must be done to ensure that the skin layer is oriented to seal against the skin layer of the other side in order to form a proper heat seal, thus adding further steps to the manufacturing process and making it more involved.
Still other types of resealable packages simply consist of an adhesive layer coated directly onto the package substrate and sealed to the other side, with minimal or no other layers between. U.S. Pat. No. 5,993,962 has a package comprising a first surface of a substrate having a strip of cold seal adhesive applied over the PSA strip, where the PSA strip is applied to a first substrate. A second substrate also contains a strip of cold seal adhesive. The first and second substrates are bonded together at the area of the cold seal adhesive and when the two areas of substrate surfaces are peeled apart to open the package, the PSA is removed from the first substrate and remains on the second substrate forming a resealable area, while the two cold seal adhesive areas remain bonded to each other. This adds an extra manufacturing step of coating a PSA and cold-seal adhesives onto the package substrates. Furthermore, such inline coating of a PSA can require additional equipment, and inline application of glue can be messy and lead to more frequent line stopping for cleaning.
Many of these known reclosable packages consist of adding an adhesive to a flexible package in the area of the seal only and/or manufacturing the package such that the adhesive is only in the area of the seal. Still other packages can heat seal against itself in only a fin seal arrangement. These can be time-consuming and difficult to do, as well as adding to the expense of manufacturing. Furthermore, as the adhesive is exposed upon opening, it is oriented towards the package interior where the food product is packaged and can be susceptible to contamination of the adhesive with the food, thus losing its adhesion and reclose properties.